JPS6026652A - Hot dip galvanized sheet for press - Google Patents

Abstract

PURPOSE:To prevent surely the formation of dent marks on dies during the press working of a galvanized sheet by specifying the amount of Fe in a layer ranging from the surface of an alloy layer along the boundary between each zinc layer of the galvanized sheet and the iron base to a position just below the zinc layer. CONSTITUTION:The amount of Fe in a layer ranging from the surface of an alloy layer along the boundary between each zing layer of a galvanized sheet and the iron base to a position just below the zinc layer is regulated to 1-6% within the range of about 40-70% of the thickness of the zinc layer. A galvanized sheet having said Fe content can be easily manufactured by adding 0.07-0.16% Al to a Zn bath for hot dipping, heating a sheet to a relatively high temp. such as about 500-540 deg.C, and introducing the sheet into the bath.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hot-dip galvanized steel sheet for press working.

[Prior art]

When press working (forming) hot-dip galvanized steel sheets,
In order to prevent zinc from adhering to the mold, press processing is performed using press oil with high lubricating properties.

[Disadvantages of conventional technology]

The plating layer of the hot-dip galvanized steel sheet has a Fe-Z layer with a thickness of approximately 3 μm or less at the boundary between the base iron (base material) of the plated original plate and the plating layer.
An n-alloy layer (Fe content of about 30%) is formed, and the rest of the surface is mostly made of zinc metal, and is therefore soft and highly adhesive.

It is accompanied by drawbacks such as the tendency for sagging to occur during press working, and the zinc in the flow part to adhere (fix) to the mold, resulting in flow restriction and a significant deterioration in quality.

[Structure of the invention]

The present invention has been made to advantageously solve these drawbacks, and its features are as follows.

The amount of Fe contained from the surface of the alloy layer at the boundary between the plating layer of the galvanized steel sheet and the iron substrate of the original sheet to just below the surface of the plating layer was 1 to 6φ. This invention relates to hot-dip galvanized steel sheets for press working.

That is, immediately below the surface of the plating layer, 40 in the thickness direction of the plating layer
~70% thickness, that is, just below the surface of the plating layer, it is sufficient to contain an amount of Fe of 1 to 6 φ.If the thickness exceeds 70 φ, a part of the alloy layer will be formed on the surface of the plating layer, which is unique to galvanized steel sheets. It is undesirable because it loses its luster, and the rust prevention effect due to the sacrificial electrode effect decreases, resulting in poor bare corrosion resistance.

Also, alloying in the lower layer of less than about 40% of the plating layer has little effect.

Next, as mentioned above, the alloy layer is made to have an Fe content of 1 to 5%, but if it is less than 1 attack, it is ineffective, and the Fe content is about 5%.
If the corrosion resistance deteriorates, the corrosion resistance may deteriorate, and alloying may progress to the vicinity of the surface of the plating layer during manufacturing, which is unsatisfactory in terms of appearance. For example, there is one method for manufacturing such a galvanized steel sheet.

Add 0.07 to 0.16% Aε in the Zn bath of the hot pickled menki bath.
The temperature of the plated original plate to be added and introduced to the public is 500~5.
It can be easily produced by increasing the temperature to 40°C. It is also possible to introduce the material into an alloying furnace and heat it after plating.

The present invention is a single-sided hot-dip galvanized steel sheet.

One side hot-dip galvanized steel sheet One side hot-dip galvanized.

On the other hand, it can be applied to alloyed galvanized steel sheets, etc.

In other words, during press working, the plated metal peels off mechanically due to galling in the die, etc.1 However, in normal (conventional) plated steel sheets, due to galling, the peeled zinc becomes soft and sticky, and the peeled zinc does not stick to each other. The particles aggregate with each other to form large particles that adhere to the mold.

This acts as a restraint on the press.

[Effect]

However, according to the present invention, configured as described above,
The pure zinc layer is thin and the plating layer is hard, making it difficult to peel off due to galling, and even when peeled off, the zinc flakes have low adhesion and do not become large particles.

It is recognized that it does not stick to the mold, and as a result, it is possible to reliably prevent the occurrence of flow restriction.

〔Effect of the invention〕

There is almost no adhesion of galvanized metal to the mold during stamping, which improves the quality of hot-dip galvanized steel sheets.

You can improve your inner side. Further, the work of removing plated metal adhering to the mold can be omitted, and the productivity of press working can be improved.

Furthermore, it is difficult for the plated surface to be blown during handling, and from this point of view as well, excellent effects such as improved quality can be obtained.

〔Example〕

Next, examples of the present invention will be listed together with comparative examples.

Note 1: The metal plate was hot-dipped zinc (normal component) plated and heated in an alloying furnace.

Note 2: The alloy layer thickness is the thickness of the alloy layer formed on top of the alloy N (2.5 μm) formed at the boundary between the plating layer and the plated original plate.

Note 3 Nibbles conditions, blank 1.00φ, punch 50φ
-5R (corner) -5,R (shoulder).

Die 53φ-5R1 presser force 400Kg.

Molded length 28 on.

As described above, according to the present invention, the adhesion of plated metal on the mold after press working was almost nonexistent, resulting in excellent results.

Claims (1)

[Claims] A hot-dip galvanized steel sheet for press working, containing 1 to 6% Fe from the surface of the alloy layer at the boundary between the plating layer and the iron substrate of the galvanized steel sheet to just below the surface of the plating layer.